Assuming you're talking about Excel or some other gultaraldehyde mix, it's not liquid CO2. It's just an inferior source of carbon. That being said, it does help if dosed at the recommended levels, but is not necessary once you get your CO2 up and running.
Of course, the use of Excel as an algae-remover is another story. Feel free to do a forum search on it. Very useful if used correctly.